Scrape off all of the surface mold around plants and discard it. According to Home Guides at SFGate, it may be necessary to re-pot potted plants with fresh, high-quality potting soil to get rid of mold. For plants in the ground, loosen the soil with a spade, tiller or gardening fork. Use a hand-held tool near the base of plants to avoid damaging the roots. Turning the soil increases drainage.